Cellulose organic acid ester plastics containing mono-tertiary-butyl hydroquinone mono-salicylate



United States Patent CELLULOSE ORGANIC ACID ESTER PLASTICS CONTAININGMONG TERTIARY- BUTYL HY- DRQQUINONE MONO-SAILICYLATE Lester W. A. Meyerand Margaret H. Eroyles, Kingsport,

Tenn., assignors to Eastman Kodak Company, Rochester, N. Y., acorporation of New Jersey No Drawing. Application November 24, 1953,Serial No. 394,201

3 Claims. (Cl. 106182) This invention relates to cellulose organic acidester plastics, and more particularly to the stabilization of suchplastics.

As is well known in the art, plastics having excellent properties for agreat many purposes can be prepared from cellulose organic acid esters,such for example, as cellulose acetate, cellulose propionate, cellulosebutyrate, cellulose acetate-propionate and cellulose acetate-butyrate,with suitable plasticizers, Many examples of suitable plasticizers areknown in the art. The choice of plasticizers forms no part of ourinvention.

However, cellulose organic acid ester plastics have not been entirelysuitable for use in places where they are exposed to a considerableamount of ultra-violet light: e. g., out of doors. After one or twomonths of outdoor exposure in a sunny climate, the plastic bleached andbecame increasingly brittle until, at the end of from three to sixmonths, depending on the severity of the climate, crazing occurred. Therapid deterioration of appearance was accompanied by an equally rapidbreakdown in physical properties, such as strength.

Some compounds whose addition to the plastic composition inhibitedphysical breakdown of the plastic, caused intense discoloration when theplastic was exposed for any length of time to sunlight or other sourceof ultra-violet light.

We have found that the addition of a small proportion ofmono-tertiary-butyl hydroquinone monosalicylate to a cellulose organicacid ester plastic composition strongly inhibits breakdown of theresulting plastic by exposure to ultraviolet light. We prefer to useapproximately 0.5% to 1% of mono-tertiary-butyl hydroquinonemono-salicylate, based on the weight of cellulose organic acid ester.Higher amounts give only slightly greater weathering resistance, and maychange the physical properties of the plastic. As cellulose organic acidesters, we have employed those mentioned above, in which the acyl groupscontain from 2 to 4 carbon atoms. Cellulose acetate plastics are not aseffective for outdoor uses as are the mixed and higher esters, that is,those containing an acyl group higher than acetyl, because the usualcellulose acetate plasticizer retention is rather poor under outdoorexposure.

Mono-tertiary-butyl hydroquinone mono-salicylate was prepared asfollows.

In a one-liter, S-necked flask fitted with an automatic decanting refluxcondenser, thermometer, and an agitator were placed 183 grams (1 mole+%excess) of monotertiary-butyl hydroquinone, 138 grams (1 mole) ofsalicylic acid and 4 drops of sulfuric acid. The mixture was fused forsix hours at 190 C., after which the 2,716,071 Patented Aug. 23, 1955The fractions were analyzed as follows:

Percent Acid 0. 49 0. 49 Melting Point C.) 67-78 80 Percent Free OH 15.34 11. 26 Theoretical percent Free OH 11.9 11.9 Theoretical percentCarbon- 71. 32 71. 32 Calculated percent Carbon 68. 17 67. 63Theoretical percent Hydrogen 6. 29 6. 29 Calculated percent Hydrogen5.18 5.00

In testing our cellulose organic acid ester plastics containing monotertiarybutyl hydroquinone mono-salicylate, we have tested sheets of0.050 inch thickness by the Kline test, designated as A. S. T. M.D795-49. The method consists of the following test cycle:

18 hours under General Electric S-l sunlamp (6 inches below lamp) 2hours in fog chamber 2 hours under S-l sunlamp 2 hours in fog chamberThis cycle was repeated until the first sign of surface failure of thesamples of plastic, as shown by dulling, chalking, checking, crazing, ordiscoloration. The temperature inside the accelerated weathering machineis maintained at to C.

It has been found by the National Bureau of Standards and verified byus, that roughly 200 hours sunlamp exposure by this test is equivalentto one years outdoor exposure in Washington, D. C. Outdoor exposurefarther south or at high altitude is more severe, however.

The following table shows the values obtained by weathering similarsamples of plasticized cellulose acetatebutyrate plastics of the samecompositions, containing (a) no ultraviolet inhibitor, (b) 1%, based onthe cellulose ester, of the well-known ultraviolet inhibitor, phenylsalicylate, and (c) 1%, based on the cellulose ester, of

mono-teritary-butyl hydroquinone mono-salicylate.

Color of Plastic Hours to Inhibitor Fallure Start of End of Test TestNone 200-250 Phenyl salicylate 1, 000 5 6 iWIono-terL-butyl hydroquinonemonosalicylate 1, 332 5 15 none monosalicylate causes no substantialdiscoloration of making up cellulose organic acid ester plasticscontaining, monotertiary-butyl hydroquinone monosalicylate.

[ Itwill be understood that this illustration does not constitute alimitation of our invention, which is defined in the appended claims.

'Example.100 parts of cellulose acetate-butyrate containingapproximately 12% acetyl and 37% butyryl is intimately mixed in asigma-blade mixer with 13 parts of dibutyl sebacate and 1 part ofmono-tertiary-butyl hydroquinone monosalicylate. The mixture is Workedon hot rolls by the method described in the Conklin Patent 2,155,303.The resulting plastic can then be granulated and be ready for anymolding or extrusion operation.

Any of the known plasticizers for cellulose organic acid esters, such,for example, as dibutyl phthalate, dibutyl sebacate, methoxyethylstearate, tricresyl phosphate, butoxyethyl phthalate, diamyl phthalate,ethyl p-toluene sulfonamide, etc. may be used. In the case of the softercellulose esters, such as cellulose acetate-butyrate, plastics mayeven'be formed Without the use of any plasticizer. o

What we claim as our inventoin and desire to:be secured by LettersPatent of the United States is:

l. A cellulose organic acid ester plastic comprising a butyrate,

cellulose organic acid ester selected from the group corisisting ofcellulose acetate, cellulose propionate, cellulose celluloseacetate-propionate and cellulose acetate-butyrate, a plasticizertherefor, and, as an agent for inhibiting deterioration of the plasticby ultra-violet light, approximately 0.5 %l%, based on the weight of Vthe cellulose ester, of 3-mono-tertiary-butyl hydroquinonemono-salicylate.

2. A cellulose acetate-butyrate plastic comprising cel luloseacetate-butyrate, a plasticizer therefor, and, as an agent forinhibiting deterioration of the plastic by ultraviolet light,approximately 0.5%l %.,based on the weight of the celluloseacetate-butyrate, of 3-mono-tertiary-butyl hydroquinone monosalicylate.V i I 3. A cellulose acetate-butyrate plastic-comprising celluloseacetate-butyrate and, as an agent for inhibiting deterioration of theplastic by ultraviolet light, approximately 0.5 %'l%, based on theweight of the cellulose acetate-butyrate, of 3-mono-tertiary-butylhydroquinone mono-salicylate.

References Cited in the file of this patent UNlTED STATES PATENTS IDreyfus Dec. 16, 1947

1. A CELLULOSE ORGANIC ACID ESTER PLASTIC COMPRISING A CELLULOSE ORGANICACID ESTER SELECTED FROM THE GROUP CONSISTING OF CELLULOSE ACETATE,CELLUOSE APROPIONATE, CELLULOSE BUTYRATE, CELLULOSE ACETATE-PROPIONATEAND CELLULOSE ACETATE-BUTYRATE, A PLASTICZER THEREFOR, AND, AS AN AGENTFOR INHIBITING DETERIORATION OF THE PLASTIC BY ULTRA-VIOLET LIGHT,APPROXIMATELY 0.5%-1% BASED ON THE WEIGHT OF THE CELLULOSE ESTER, OF3-MONO-TERTIARY-BUTYL HYDROQUINONE MONO-SALICYLATE.